low-Na Diet Research Articles

Abstract 129: Ngal Is A Novel Target In Hypertension By Modulating The Ncc-mediated Renal Na Balance

Background: The expression of neutrophil gelatinase-associated lipocalin (NGAL/lcn2) is directly modulated by mineralocorticoid receptor activation but its role in blood pressure control is unclear. Methods: a potential relationship between NGAL plasma levels, systolic blood pressure and urinary Na excretion was assessed in the STANISLAS cohort. The specific role of NGAL/lcn2 in salt-sensitive hypertension was studied using lcn2-depleted mice (lcn2 KO) fed with low Na diet (0Na). Results: we show that NGAL plasma levels positively correlate with systolic blood pressure (SBP), whereas they negatively correlate with urinary Na excretion in subjects of the STANISLAS cohort. Prolonged feeding of lcn2 KO mice with a 0Na diet induced lower SBP than that of the control group (WT), suggesting a role for NGAL/lcn2 in Na-balance homeostasis. Short-term or prolonged 0Na increased Na-Cl cotransporter (NCC) phosphorylation in the cortex of WT mice, which was prevented in lcn2 KO mice. Recombinant mouse lcn2 injections in lcn2 KO mice induced NCC phosphorylation in the kidney cortex, associated with decreased urinary Na excretion. Ex-vivo experiments using kidney slices from lcn2 KO mice showed increased NCC phosphorylation by recombinant murine lcn2. In addition, recombinant murine lcn2 induced activation of CamK2β phosphorylation in lcn2 KO mice and in kidney slices, providing an underlying mechanism involved in lcn2-induced NCC phosphorylation. Indeed, the inhibition of CamK2β prevented NCC phosphorylation induced by recombinant lcn2 in kidney slices. Conclusion: we highlight a novel role of NGAL/lcn2 as a modulator of the activity of the renal sodium transporter NCC affecting salt-sensitive blood pressure

NGAL is a Novel Target in Hypertension by Modulating the NCC-Mediated Renal Na Balance.

The expression of NGAL/lcn2 (neutrophil gelatinase-associated lipocalin) is directly modulated by mineralocorticoid receptor activation but its role in blood pressure control is unclear. a potential relationship between NGAL plasma levels, systolic blood pressure and urinary Na excretion was assessed in the STANISLAS cohort. The specific role of NGAL/lcn2 in salt-sensitive hypertension was studied using lcn2-knockout mice (lcn2 KO) fed with low-Na diet (0Na). we show that NGAL plasma levels positively correlate with systolic blood pressure, whereas they negatively correlate with urinary Na excretion in subjects of the STANISLAS cohort. Prolonged feeding of lcn2 KO mice with a 0Na diet induced lower systolic blood pressure than that of the control group (wildtype), suggesting a role for NGAL/lcn2 in Na-balance homeostasis. Short-term or prolonged 0Na increased Na-Cl cotransporter (NCC) phosphorylation in the cortex of wildtype mice, which was prevented in lcn2 KO mice. Recombinant mouse lcn2 injections in lcn2 KO mice induced NCC phosphorylation in the kidney cortex, associated with decreased urinary Na excretion. Ex vivo experiments using kidney slices from lcn2 KO mice showed increased NCC phosphorylation by recombinant murine lcn2. In addition, recombinant murine lcn2 induced activation of CamK2β (calcium/calmodulin-dependent protein kinase II β subunit) phosphorylation in lcn2 KO mice and in kidney slices, providing an underlying mechanism involved in lcn2-induced NCC phosphorylation. Indeed, the inhibition of CamK2β prevented NCC phosphorylation induced by recombinant lcn2 in kidney slices. we highlight a novel role of NGAL/lcn2 as a modulator of the activity of the renal sodium transporter NCC affecting salt-sensitive blood pressure.

Results of Salt Intake Restriction Monitored with the New Sodium Control Biosensor

Introduction: Adherence to a low-sodium (Na) diet is crucial in patients under hemodialysis, as it improves cardiovascular outcomes and reduces thirst and interdialytic weight gain. Recommended salt intake is lower than 5 g/day. The new 6008 CAREsystem monitors incorporate a Na module that offers the advantage of estimating patients’ salt intake. The objective of this study was to evaluate the effect of dietary Na restriction for 1 week, monitored with the Na biosensor. Methods: A prospective study was conducted in 48 patients who maintained their usual dialysis parameters and were dialyzed with a 6008 CAREsystem monitor with activation of the Na module. Total Na balance, pre-/post-dialysis weight, serum Na (sNa), changes in pre- to post-dialysis sNa (ΔsNa), diffusive balance, and systolic and diastolic blood pressure were compared twice, once after 1 week of patients’ usual Na diet and again after another week with more restricted Na intake. Results: Restricted Na intake increased the percentage of patients on a low-Na diet (<85 Na mmol/day) from 8% to 44%. Average daily Na intake decreased from 149 ± 54 to 95 ± 49 mmol, and interdialytic weight gain was reduced by 460 ± 484 g per session. More restricted Na intake also decreased pre-dialysis sNa and increased both intradialytic diffusive balance and ΔsNa. In hypertensive patients, reducing daily Na by more than 3 g Na/day lowered their systolic blood pressure. Conclusions: The new Na module allowed objective monitoring of Na intake, which in turn could permit more precise personalized dietary recommendations in patients under hemodialysis.

Low Sodium Supply in Early Life Causes Growth Restriction and Programs Long‐Term Changes in Energy Homeostasis

Preterm birth is a risk factor for the development of a multitude of diseases later in life. Preterm infants are also at risk for growth failure following parturition, which further compounds the adverse effects of preterm birth. Previous studies have shown that prematurely born human infants’ kidneys are inefficient at retaining sodium, therefore putting these infants at high risk of sodium depletion. We have developed a “post‐wean” dietary manipulation to model early‐life sodium depletion. In this model, mice are fed variations of soy‐free 2920x diet (Teklad); low‐sodium (0.04% Na, n=6), or high/normal‐sodium (0.30% Na, n=8), from weaning at week three of life, until week six of life. At six weeks of age, all mice are switched back to the “standard” 2920x diet (0.15% Na). Food and water intake behaviors, physical activity, energy expenditure, and body composition of the mice were serially analyzed using a multiplexed phenotyping system (Promethion, Sable Systems International) and time‐domain nuclear magnetic resonance (NMR; Bruker LF110). Mice supplied low‐Na between 3‐6 weeks of age exhibited delayed growth during weeks 3‐6, then rapid “catch‐up growth” following return to “normal” diet in week 6, and similar growth kinetics to the high‐Na group thereafter (diet x age interaction p&lt;0.01). The delay in body mass expansion in the low‐Na group was due to a decrease in fat‐free mass (diet x age interaction p&lt;0.01). Mice fed low‐Na diet exhibited reduced food intake (diet p&lt;0.01), due to slower eating speed (diet p&lt;0.01) and meal size (diet p=0.01). The reduced food intake relative to body composition was sustained through 18 weeks of age (diet x age interaction p=0.93). Water intake was also increased in mice treated with low‐Na diet both during diet intervention and through 18 weeks of age (diet p&lt;0.01), due to an increased number of drinking bouts (diet p&lt;0.01) of comparable size (diet p=0.46). Total aerobic energy expenditure was increased in mice fed the low‐Na diet, even after correction for body composition (diet p&lt;0.01). Mice treated with low‐Na diet in early life also exhibited an increase in energy expenditure that was maintained through 18 weeks of age (diet x age p&gt;0.99), even after correction for body composition and for differences in food intake. Finally, mice treated with low‐Na diet demonstrate a reduction in calories that are unaccounted for by these methods (diet p&lt;0.01, diet x age interaction p=0.68). In conclusion, post‐wean sodium depletion causes growth failure and changes in body composition that parallel premature human infant growth failure. Profoundly, this relatively simple 3‐week diet switch causes changes in intake behaviors and energy expenditure that are then “programmed” for at least another 12 weeks after switch back to a “normal” diet. These findings support our working hypothesis that early‐life sodium supply impacts energy homeostasis and growth kinetics and prompts reconsideration of current guidelines concerning sodium supplementation to prematurely born and low‐birthweight infants.

Can fractional excretion of sodium predict worsening of renal function, in-hospital mortality, and length of hospital stay in acute decompensated heart failure?

BACKGROUNDFractional excretion of sodium (FENa), the reflection of sodium (Na) handling by the kidney during natriuresis, is influenced by exo- and endogenous factors that have a powerful impact on renal function. We performed this study to define the correlation between FENa and worsening renal function (WRF) and assess the value of FENa in the length of hospital stay and in-hospital mortality in the patients with acute decompensated heart failure (ADHF).METHODSThis prospective observational study was performed in two tertiary governmental heart centers located in Ahvaz, Iran, from March 2019 to March 2020. Any individual suffering from ADHF who had no renal failure, received only loop diuretics, and was on a low Na diet was eligible for recruitment in this study. The urine sample used to calculate FENa was a 24-hour sample.RESULTSOver the one year, 56 patients met the inclusion criteria. The total study population had a mean age of 61.46 ± 14.22 years with the dominance of women (51.8%). The mean age of men and women was 58.59 ± 14.35 and 64.13 ± 13.80 years, respectively. During hospitalization, 13 (23.2%) patients experienced WRF. In patients who experienced WRF during hospitalization, FENa of < 1% was mostly observed compared to FENa of 1%-2% (42.9% vs. 0%, P < 0.05). Post-hoc test of data on mean hospitalization days indicated that those with lower FENa had longer admission periods than those with other FENa groups (< 1%: 3.04 ± 1.02 days vs. 1%-2%: 1.58 ± 0.66 days, P < 0.001 and < 1%: 3.04 ± 1.02 days vs. > 2%: 2.30 ± 0.92 days, P = 0.02). There was no significant relation in terms of in-hospital death across different categories of FENa (P = 0.69).CONCLUSIONOur data suggested that FENa less than 1% was associated with WRF and could be associated with a longer hospitalization period. We did not find any association between FENa and in-hospital mortality. Further studies with a larger number of patients are required to determine the cut-off value.

Follow-up on new marker confirming the optimal status in the treatment of heart failure with reduced ejection fraction

Abstract Background At the present time, there is no strong criterion to guarantee the optimal management for patients with heart failure and reduced ejection fraction (HFrEF). In the past, our group suggested the use of the size of the femoral vein (FV), measured by ultrasound as a marker of the fluid status in the venous compartment. Is this criterion still the best marker of optimal treatment of HFrEF at 3 years follow-up, especially for patients with significant co-morbidities (chronic obstructive pulmonary disease (COPD), end stage renal disease (ESRD) on hemodialysis (HD), cirrhosis of liver or sepsis? Methods Patients with HFrEF and co-morbidities as above were enrolled. All patients had echocardiography to confirm EF &amp;lt;45% and underwent the ultrasound test to assess the size and expansibility of the femoral vein (SEFV). The SEFV is the ultrasound study of the FV examining its size and expansibility with cough. The location of the femoral artery (FA) and FV to be checked is the coronal plane immediately proximal to the bifurcation of the superficial and deep femoral artery. The normal size of FV is a little larger than of the FA. If the size of the FV is twice larger than the FA, the patient has fluid overload in the venous compartment (Figure 1). Then the patient was asked to cough in order to measure the size of the FV. If the FV did not increase its size with cough, the venous compartment was full. If the FV increased its size, the venous compartment was not full and could accommodate more fluid. In physical exam, the fluid overload is proved by the presence of extravascular fluid in the abdominal wall, ascites or leg edema or in the intravascular compartment by the presence of the jugular venous distention. During the 3 years of follow-up, the patients were seen in the office and had the SEFV at regular 6 months intervals. A small group of patients also underwent right heart catheterization to measure to the pulmonary capillary wedge pressure (PCWP). Results 180 patients with HFrEF and significant comorbidities were enrolled. All patients were taught to follow a low Na diet, &amp;lt;2000cc of fluid restriction and the guideline directed medical therapy. After about 3 years, 75% patients in the study group were asymptomatic, was not readmitted to the hospital for HF, and the size of the FV was within normal range. Their physical exam showed no fluid in the extravascular compartment. The PCWP became lower than 24mmHg in 18/20 who underwent the RHC. There was significant weight loss (15 lbs). In the control group, 60% of patients were asymptomatic and 50% were not readmitted for HF (p&amp;lt;0.05). Conclusions With the SEFV test, the patients with HFrEF and significant comorbidities were accurately estimated for presence or absence of fluid overload. This SEFV test was especially sensitive to detect fluid overload in patients with multiple co-morbidities. Further randomized trials are needed to confirm the above preliminary results. Funding Acknowledgement Type of funding sources: None. Figure 1. Enlarged size of femoral vein

Dissociable effects of dietary sodium in early life upon somatic growth, fluid homeostasis, and spatial memory in mice of both sexes.

Postnatal growth failure is a common morbidity for preterm infants and is associated with adverse neurodevelopmental outcomes. Although sodium (Na) deficiency early in life impairs somatic growth, its impact on neurocognitive functions has not been extensively studied. We hypothesized that Na deficiency during early life is sufficient to cause growth failure and program neurobehavioral impairments in later life. C57BL/6J mice were placed on low- (0.4), normal- (1.5), or high- (3 g/kg) Na chow at weaning (PD22) and continued on the diet for 3 wk (to PD40). Body composition and fluid distribution were determined serially by time-domain NMR and bioimpedance spectroscopy, and anxiety, learning, and memory were assessed using the elevated plus maze and Morris water maze paradigms in later adulthood (PD63-PD69). During the diet intervention, body mass gains were suppressed in the low- compared with normal- and high-Na groups despite similar caloric uptake rates across groups. Fat mass was reduced in males but not in females fed low-Na diet. Fat-free mass and hydration were significantly reduced in both males and females fed the low-Na diet, although rapidly corrected after return to normal diet. Measures of anxiety-like behavior and learning in adulthood were not affected by diet in either sex, yet memory performance was modified by a complex interaction between sex and early life Na intake. These data support the concepts that Na deficiency impairs growth and that the amount of Na intake which supports optimal somatic growth during early life may be insufficient to fully support neurocognitive development.

Abstract P218: Dietary Prescription in the Coronary Care Unit, Missed Opportunity to Improve Care?

Introduction: A notable portion of the excess burden of cardiovascular disease [CVD] risk factors in African Americans [AA] is believed secondary to the diet. Hypothesis: Dietary assessment and prescribed diets are inadequate in patients admitted to the coronary care unit [CCU]. Results: Cohort: 267 consecutively patients, AA 83%, male 55%, mean age 65 yrs, were assessed for cardiovascular [CV] risk factors, clinical status and appropriateness of prescribed diets. Patients were at increased CV risk as evidenced by 65% older than 60 yrs, Body Mass Index (BMI) &gt;30 in 40% with women almost twice as likely to be obese [p&lt;0.006], history of smoking 55%, hypertension 90%, diabetes 54%, and mean ejection fraction 43%. Established CAD acknowledged in 60%. Breakdown of diet orders: normal diet 11%, diabetic diet 38% and a form of low sodium, low cholesterol diet in 51%. CCU length of stay: 2.5 days with no significant difference by sex, diabetic or obesity status. Dietary assessment documentation was missing in 40% of the CCU admissions. A significant percentage of the patients missing this documentation were women [45%], diabetics [47%], obese--BMI&gt;30 [42%] and older--age &gt;60 [68%]. Incongruence is seen between the disease burden and the appropriate dietary order. For example, 54% of patients had DM. However, only 38% were given a diabetic diet. A form of low Na diet was provided to 51% of the patients yet 90% of them were hypertensive or had a history of hypertension. The statistic, dietary assessment not recorded in 40% of the patients, may have been affected by the relatively short CCU stay. One limitation of our study is that we did not examine if this decreased dietary assessment rate was affected by week-day vs. weekend stay in the CCU or by the severity of the patient’s illness. Conclusion: Dietary assessment and appropriate dietary prescription matters. Recent studies show that dietary pattern is one of the largest mediating factors for differences in the incidence of CV risks, i.e. hypertension, in blacks vs. whites accounting for some of the excess risk among blacks. Not adequately addressing nutrition in a CCU setting leads to the loss of a critical teachable moment.

Determination of bone sodium (Na) and Na exchange in pig leg using in vivo neutron activation analysis (IVNAA)

Objective: The locations of sodium (Na) storage and its exchange mechanisms in the body are not well known. Understanding tissue Na storage and exchange is important for understanding the impact of Na intake, absorption, and retention on human health, especially on the risk of developing chronic diseases. The purpose of this study was to investigate the application of a deuterium–deuterium (DD) neutron generator-based IVNAA system in Na nutrition studies. Approach: The right legs of two live pigs, one on a low Na diet and one on a high Na diet, both for 14 d, were irradiated inside a customized irradiation cave for 10 min (45 mSv dose to the leg) and then measured with a 100% efficient high purity germanium detector (HPGe). The spectra were analyzed to obtain the net Na counts at different time points. Bone Na concentrations were calculated using the calibration created with Na bone phantoms. Main results: The results show that the difference in bone Na to calcium between the pigs on high versus low Na diets was 466 ± 137 ppm. The estimated bone Na to calcium concentrations were 1166 ± 80 and 1631 ± 111 ppm for low and high Na diet pigs, respectively. Analysis also shows rapid exchange of Na in the leg during the first 2 h measurements, while the exchange was minimal at the second and third 2 h measurements, taken 7 and 21 h post irradiation. The exchange decay time of Na in the leg was 51 min for the first measurement, and there was no significant change of Na activities between 2–21 h. Significance: With these results, we conclude there is a non or low exchangeable compartment (likely to be bone) for Na storage and that DD neutron generator-based IVNAA is a useful method for determining tissue Na distribution in nutrition studies.

Response of broiler chickens to diets containing different levels of sodium with or without microbial phytase supplementation.

Phytate induced excessive mineral excretion through poultry litter leads to poor performance and environmental pollution. Exogenous microbial phytase supplementation to poultry diets reduce the environmental excretion of nutrient and improve bird’s performance. However, excessive dietary sodium (Na) level may hinder the phytase-mediated phytate hydrolysis and negate the beneficial effects of phytase. Therefore, this experiment was conducted to investigate the effects of different concentration dietary Na on phytase activity and subsequent impact on broiler performance, bone mineralisation and nutrient utilisation. In this study, six experimental diets, consisting of three different levels of Na (1.5, 2.5, or 3.5 g/kg) and two levels of microbial phytase (0 or 500 U/kg) were formulated by using 3 × 2 factorial design. The six experimental diets were offered to 360 day-old Ross 306 male chicks for 35 days, where, each experimental diet consisted of 6 replicates groups with 10 birds. Along with growth performance, nutrient utilization, intestinal enzyme activity, dry matter (DM) content of litter and mineral status in bone were analysed. Dietary Na and phytase had no effect on bode weight gain and feed intake. Birds on the low Na diet showed higher (p < 0.05) feed conversion ratio (FCR) than the mid-Na diets. High dietary Na adversely affected (p < 0.001) excreta DM content. Phytase supplementation to the high-Na diet increased (p < 0.01) the litter ammonia content. High dietary Na with phytase supplementation improved (Na × phytase, p < 0.05) the AME value and ileal digestibility of Ca and Mg. The total tract retention of Ca, P, and Mg was reduced with high Na diet, which was counteracted by phytase supplementation (Na × phytase, p < 0.001). The diets containing mid-level of Na improved (p < 0.001) the function of Na-K-ATPase and Mg-ATPase in the jejunum. The overall results indicate that high dietary Na did not affect phytase activity but influenced the nutrient utilization of birds, which was not reflected in bird overall performance.

Low Sodium Diet Decreases Stone Formation in Genetic Hypercalciuric Stone-Forming Rats

Background: Urine (u) calcium (Ca) excretion is directly dependent on dietary sodium (Na) intake leading to the recommendation for Na restriction in hypercalciuric kidney stone formers. However, there is no direct evidence that limiting Na intake will reduce recurrent stone formation. Materials and Methods: We used genetic hypercalciuric stone-forming (GHS) rats, which universally form Ca phosphate (P) kidney stones, fed either a low Na (LNa, 0.05%) or normal Na (NNa, 0.4%) Na diet (D) for 18 weeks. Urine was collected at 6-week intervals. Radiographic analysis for stone formation and bone analyses were done at the conclusion of the study. Results: Mean uCa was lower with LNaD than NNaD as was uP and LNaD decreased mean uNa and uChloride. There were no differences in urine supersaturation (SS) with respect to calcium phosphate (CaP) or Ca oxalate (CaOx). However, stone formation was markedly decreased with LNaD by radiographic analysis. The LNaD group had significantly lower femoral anterior-posterior diameter and volumetric bone mineral density (vBMD), but no change in vertebral trabecular vBMD. There were no differences in the bone formation rate or osteoclastic bone resorption between groups. The LNaD group had significantly lower femoral stiffness; however, the ultimate load and energy to fail was not different. Conclusion: Thus, a low Na diet reduced uCa and stone formation in GHS rats, even though SS with respect to CaP and CaOx was unchanged and effects on bone were modest. These data, if confirmed in humans, support dietary Na restriction to prevent recurrent Ca nephrolithiasis.

Salt, Hypertension, and the Lens.

Salt is important in the pathogenesis of hypertension (HT). Salt-sensitive hypertension (SSH) accounts for about half of all HT cases. In SSH, sodium/potassium adenosine triphosphatase (Na+/K+-ATPase) activity is impaired. Impaired Na+/K+-ATPase activity in the lens epithelium results in cortical opacities in the peripheral equator of the lens. We investigated the sensitivity of cortical lens opacities in detecting SSH. The study included 191 SSH and 159 non-SSH, salt-resistant HT (SRH) patients (350 HT patients total), aged 40-80 years. One hundred twenty-four sex- and age-matched patients without a HT diagnosis made up the control group. Daily salt intake of all groups was calculated from 24-hr urinary Na excretion. SSH was diagnosed when the difference in mean arterial blood pressure values obtained during high- and low-Na diets was ≥10%. Non-SSH, SRH was diagnosed when the difference was <10%.Two researchers examined the presence of cortical lens opacities biomicroscopically using the diffuse, direct, Scheimpflug, and retroillumination from fundus methods. Total lens opacity was predictive of SSH among all cases (P < 0.001), with a sensitivity and specificity of 75.4% [95% confidence interval (CI): 68.6-81.3] and 83.6% (95% CI: 77.0-89.0), respectively. Its positive and negative predictive values were 84.7% (95% CI: 79.4-88.8) and 73.9% (95% CI: 68.6-78.5), respectively. Lens opacities can be used as a finding that can be easily observed in the detection of SSH and excess salt intake.

Abstract P330: Customization of Low-sodium Diet and Its Efficacy

Introduction: Lack of adherence with a low-sodium (Na) diet remains a challenge for many patients. Most research studies use standardized diets for subjects which may decrease adherence and hence result in sub-optimal lowering of blood pressure (BP). We hypothesized that adoption of a customized low-Na diet will result in high rates of adherence, lower BP, and improve vascular function. Methods: Post-menopausal women (50-65 years) and men (30-65 years) with baseline BP ≥ 130/80 mm Hg or history of HTN were recruited. Subjects were placed on a 2-week 1200mg Na/day diet (after a 3-day run-in period during which subjects were given 2400 mg of Na/day in addition to their regular diet). Subjects were off all BP medications 1 week prior to the start of the diet and during 2 weeks of study diet. All food was prepared by a bio-nutritionist with a customized menu according to food logs kept by the subjects. Two 24h urine Na measurements were taken to ensure compliance with the diet. In addition to BPs, conduit (brachial artery flow-mediated dilation (FMD)) and micro (~ 200 μm extracted from gluteal adipose tissue biopsies) vessel functions were evaluated before and after the diet period to assess in vivo and in vitro vascular function respectively. Results: Seventeen subjects (9 African-American, 7 Caucasian, and 1 Hispanic) with mean BPs of 145 ± 14/87 ± 6 mm Hg (± SD) before starting the low-Na diet were recruited. During the diet period, subjects consumed an average of 1000 mg of Na/day (66% reduction from baseline Na intake). Excluding 2 subjects in whom the 24h urine Na did not drop (instead increased) after 2-weeks indicating non-adherence, the average SBP/DBP reductions were -11 ± 14 (-7%, p=0.06)/-8 ± 10 mm Hg (-9%, p=0.04). Average urine Na levels were 230 ± 83 (before) and 71 ± 82 (after) mmol/24hr. Brachial artery FMD improved from 7.3 ± 3.2 to 9.6 ± 2.3 % (p=0.04) after 2 weeks. Maximal Arteriolar FMD (endothelial dependent) trended toward an increase from 54 ± 18 to 77 ± 13 % and smooth muscle dependent dilation to papaverine was not effected. Conclusions: The adoption of a customized low-Na diet can result in high rates of dietary adherence (88% in the current study) and lower BPs. In addition, vascular function improves within 2 weeks on a low-Na diet.

Partial substitution of sodium chloride by potassium chloride in bread: effect on dough and bread properties

Negative effect of sodium chloride (NaCl) consumption to health has been forcing food processors to re-formulate their products for possible reduction of Na. Reducing Na content of bread, without compromising its sensory-textural properties and the process requirements, might lead to start a low Na diet. While innovative approaches are continuously introduced for Na reduction in processed foods, a common approach is the use of various cations, like potassium, as Na substitutes. Therefore, the objective of this study was to determine the replacement ratio of NaCl with KCl in an industrial white bread production. For this purpose, white bread loaves with partial replacement of NaCl were produced using the straight-dough method. Textural properties of dough samples and sensory properties of bread loaves were determined. Bread with NaCl replacement up to 37.5% KCl was determined to have similar sensory characteristics as the control bread samples. Moreover, no significant impact on dough properties (extensibility, stickiness) was observed. Considering the convenience of replacing NaCl with KCl in industrial production and reducing Na-intake this simple approach might help preventing further health related problems.

Na(+) dependence of K(+) -induced natriuresis, kaliuresis and Na(+) /Cl(-) cotransporter dephosphorylation.

High dietary K(+) intake is associated with protection against hypertension. In mammals, acute K(+) intake induces natriuresis and kaliuresis, associated with a marked dephosphorylation of the renal Na(+) /Cl(-) cotransporter (NCC). It has been suggested that reduced activity of NCC increases the driving force for more distal tubular epithelial Na(+) channel (ENaC)-dependent K(+) secretion. This study investigated the ENaC dependence of urinary K(+) and Na(+) excretion following acute K(+) loading. Mice were fed low (0.03%), control (0.2%) or high (2%) Na(+) diets for 25days to preserve or promote Na(+) loss and thus ENaC activity. Once a week, the mice received either K(+) -containing gavage or a control gavage. Following the gavage treatment, the mice were placed in metabolic cages and urine was collected in real time. ENaC dependence of kaliuresis was assessed by benzamil injections prior to gavage. We confirmed that dietary Na(+) content is inversely related to plasma aldosterone, NCC phosphorylation and ENaC cleavage products. The novel findings were as follows: (i) acute K(+) feeding caused NCC dephosphorylation in all dietary groups; (ii) under all dietary conditions, K(+) loading induced natriuresis; (iii) high Na(+) diet markedly reduced the K(+) excretion following K(+) gavage; (iv) benzamil injection prior to K(+) loading increased natriuresis, decreased kaliuresis and eliminated the differences between the dietary groups. These data indicate that acute K(+) -induced kaliuresis is ENaC dependent. Maximal K(+) excretion rates are attenuated when ENaC is physiologically down-regulated or pharmacologically blocked. NCC is dephosphorylated following acute K(+) loading under all dietary Na(+) regimens. This leads to natriuresis, even in severely Na(+) -restricted animals.

Effects of dietary NaCl on the in vivo apparent absorption of dietary nutrients determined in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (mean body weight 52.3g) were reared in freshwater and fed a semi-purified low-sodium (Na) diet (Na content 0.027%) or NaCl-supplemented diets (Na content 0.35% and 1.75%). The chyme of the proximal and distal intestines of fish were collected by dissection. The diets and chyme were analyzed, and apparent digestibility (net absorption) and indigestibility of dietary nutrients was estimated based on yttrium as a reference. Na concentration of the intestinal chyme, both proximal and distal regions, was similar regardless of dietary Na levels. A major Na secretion into the proximal lumen was noted in fish fed the low-Na diet. The net phosphorus (P) absorption was already ~90% at the proximal intestine, but dietary Na had no detectable effect on net P absorption, both in the proximal and distal intestine. The Ca content was more than two times higher in the distal than the proximal chyme. Dietary Na had no effect on chyme Ca content, but tended to increase Mg content in the proximal and distal chyme. There was no apparent effect of dietary Na on net Fe and Zn absorption in the proximal and distal intestine. Dietary Na decreased net absorption of Mn. Dietary Na tended to increase dry matter and organic carbon digestibilities in the distal intestine. Digestibility of crude protein (CP) was increased by dietary Na in the proximal, but not distal, region. These results collectively indicate that dietary Na may slightly increase digestibilities of macronutrients in rainbow trout reared in freshwater. Statement of relevanceSodium (Na) is an important ion for dietary nutrient absorption in the intestine. However, the effect of dietary Na on an in vivo nutrient absorption efficiency has been little studied in fish. Hence, we evaluated the effect of dietary NaCl on nutrient digestibility (absorption) in rainbow trout reared in freshwater.

Possible role for nephron-derived angiotensinogen in angiotensin-II dependent hypertension.

The role of intranephron angiotensinogen (AGT) in blood pressure (BP) regulation is not fully understood. Previous studies showed that proximal tubule-specific overexpression of AGT increases BP, whereas proximal tubule-specific deletion of AGT did not alter BP. The latter study may not have completely eliminated nephron AGT production; in addition, BP was only assessed on a normal salt diet. To evaluate this issue in greater detail, we developed mice with inducible nephron-wide AGT deletion. Mice were generated which were hemizygous for the Pax8-rtTA and LC-1 transgenes and homozygous for loxP-flanked AGT alleles to achieve nephron-wide AGT disruption after doxycycline induction. Compared to controls, AGT knockout (KO) mice demonstrated markedly reduced renal AGT immunostaining, mRNA, and protein levels; unexpectedly AGT KO mice had reduced AGT mRNA levels in the liver along with 50% reduction in plasma AGT levels. BP was significantly lower in the AGT KO mice compared to controls fed a normal, low, or high Na(+) intake, with the highest BP reduction on a low Na(+) diet. Regardless of Na(+) intake, AGT KO mice had higher plasma renin concentration (PRC) and markedly reduced urinary AGT levels compared to controls. Following angiotensin-II (Ang-II) infusion, AGT KO mice demonstrated an attenuated hypertensive response despite similar suppression of PRC in the two groups. Taken together, these data suggest that nephron-derived AGT may be involved in Ang-II-dependent hypertension, however, a clear role for nephron-derived AGT in physiological BP regulation remains to be determined.

The Vacuolar H+-ATPase B1 Subunit Polymorphism p.E161K Associates with Impaired Urinary Acidification in Recurrent Stone Formers.

Mutations in the vacuolar-type H(+)-ATPase B1 subunit gene ATP6V1B1 cause autosomal-recessive distal renal tubular acidosis (dRTA). We previously identified a single-nucleotide polymorphism (SNP) in the human B1 subunit (c.481G>A; p.E161K) that causes greatly diminished pump function in vitro To investigate the effect of this SNP on urinary acidification, we conducted a genotype-phenotype analysis of recurrent stone formers in the Dallas and Bern kidney stone registries. Of 555 patients examined, 32 (5.8%) were heterozygous for the p.E161K SNP, and the remaining 523 (94.2%) carried two wild-type alleles. After adjustment for sex, age, body mass index, and dietary acid and alkali intake, p.E161K SNP carriers had a nonsignificant tendency to higher urinary pH on a random diet (6.31 versus 6.09; P=0.09). Under an instructed low-Ca and low-Na diet, urinary pH was higher in p.E161K SNP carriers (6.56 versus 6.01; P<0.01). Kidney stones of p.E161K carriers were more likely to contain calcium phosphate than stones of wild-type patients. In acute NH4Cl loading, p.E161K carriers displayed a higher trough urinary pH (5.34 versus 4.89; P=0.01) than wild-type patients. Overall, 14.6% of wild-type patients and 52.4% of p.E161K carriers were unable to acidify their urine below pH 5.3 and thus, can be considered to have incomplete dRTA. In summary, our data indicate that recurrent stone formers with the vacuolar H(+)-ATPase B1 subunit p.E161K SNP exhibit a urinary acidification deficit with an increased prevalence of calcium phosphate-containing kidney stones. The burden of E161K heterozygosity may be a forme fruste of dRTA.

Critical role of the SPAK protein kinase CCT domain in controlling blood pressure.

The STE20/SPS1-related proline/alanine-rich kinase (SPAK) controls blood pressure (BP) by phosphorylating and stimulating the Na-Cl (NCC) and Na-K-2Cl (NKCC2) co-transporters, which regulate salt reabsorption in the kidney. SPAK possesses a conserved carboxy-terminal (CCT) domain, which recognises RFXV/I motifs present in its upstream activator [isoforms of the With-No-lysine (K) kinases (WNKs)] as well as its substrates (NCC and NKCC2). To define the physiological importance of the CCT domain, we generated knock-in mice in which the critical CCT domain Leu502 residue required for high affinity recognition of the RFXI/V motif was mutated to Alanine. The SPAK CCT domain defective knock-in animals are viable, and the Leu502Ala mutation abolished co-immunoprecipitation of SPAK with WNK1, NCC and NKCC2. The CCT domain defective animals displayed markedly reduced SPAK activity and phosphorylation of NCC and NKCC2 co-transporters at the residues phosphorylated by SPAK. This was also accompanied by a reduction in the expression of NCC and NKCC2 protein without changes in mRNA levels. The SPAK CCT domain knock-in mice showed typical features of Gitelman Syndrome with mild hypokalaemia, hypomagnesaemia, hypocalciuria and displayed salt wasting on switching to a low-Na diet. These observations establish that the CCT domain plays a crucial role in controlling SPAK activity and BP. Our results indicate that CCT domain inhibitors would be effective at reducing BP by lowering phosphorylation as well as expression of NCC and NKCC2.

NEPHRON SPECIFIC DELETION OF PRORENIN RECEPTOR MODULATES WATER AND SODIUM HOMEOSTASIS

The prorenin receptor (PRR), a newly discovered component of the RAS, has been localized to the collecting duct, distal convoluted tubule, proximal tubule and podocytes. Targeted deletion of PRR, whether global or cell-specific, has resulted in either early lethality or organ malformation due to abnormal lysosomal acidification. Consequently, the physiological significance of nephron derived PRR is unclear. To examine this, we developed mice with inducible nephron-wide PRR deletion. Mice were generated which were hemizygous for the Pax8-rtTA and LC-1 transgenes and homozygous for loxP flanked PRR alleles to achieve nephron-specific PRR disruption after doxycycline induction. Adult Pax8-rtTA/LC-1/floxed PRR mice were treated with doxycycline 2 mg/ml in drinking water for 12 days and studied 4 weeks after treatment. Nephron specific PRR KO mice have normal survival and no histological defects in the kidney. Compared to controls, PRR knockout (KO) mice demonstrated 60% lower PRR mRNA levels and significantly lower PRR immunofluorescence. Under both Na intake, PRR KO mice had significantly lower urine osmolality, higher water intake and higher urine volume compared to controls. No notable differences were seen in body weight or food intake. PRR KO mice had higher Na excretion compared to controls on days 1 and 2 of change from normal to low Na diet but similar Na excretion on other days of low Na intake. Finally, no detectable differences in BP were noted between the two groups on normal or low Na diet (7 days each). These data suggest that nephron PRR can potentially modulate water and sodium homeostasis. * P < 0.05 Normal Na diet (0.25%) lLow Na diet (0.03%) Controls PRR KO Controls PRR KO Body weight (g) 26.9 ± 3.1 24.2 ± 1.6 26.3 ± 2.7 23.3 ± 1.4 Food intake (g) 5.2 ± 0.3 4.4 ± 0.3 4.0 ± 0.3 3.8 ± 0.3 Water intake (ml) 3.9 ± 0.6 8.9 ± 1.3* 3.9 ± 0.4 7.2 ± 0.8* Urine Volume (ml/day) 1.7 ± 0.2 6.0 ± 1.0* 1.3 ± 0.4 4.4 ± 0.7* Urine osmolality (mosm Kg/H2O) 3133 ± 396 1325 ± 426* 1679 ± 270 976 ± 320* Urine NaV (μmol/d) 222 ± 28 236 ± 32 42 ± 6 66 ± 10* Urine KV(μmol/d) 311 ± 32 298 ± 28 184 ± 31 236 ± 20 Systolic blood pressure (mm Hg) 119 ± 3 122 ± 4 118 ± 4 122 ± 2 Diastolic blood pressure (mm Hg) 94 ± 3 96 ± 3 93 ± 2 95 ± 3